1. Field Of The Invention
The present invention relates to the field of inflatable prostheses and tissue expanders.
2. Description Of Related Art
Inflatable mammary prostheses and tissue expanders are well known in the prior art. In the case of an inflatable mammary prosthesis, the prosthesis is normally inserted through a small incision substantially under the patient's arm. To allow the prosthesis to pass through the small incision, the air filled prosthesis is normally substantially deflated by aspirating the same with an empty, sterile syringe. At this point, some surgeons prefer to add some of the intended inflation fluid to the prosthesis, primarily to displace the remaining air with fluid as opposed to inflating the prosthesis to any substantial extent. In any event, then the prosthesis is folded and inserted into a surgically prepared pocket. Once implanted of course, the prosthesis must be inflated to provide the desired resulting aesthetic appearance.
The conventional method of inflating a breast prosthesis, once implanted, is to use a conventional syringe to inject the filling fluid through an appropriate fill port on the prosthesis. Since a mammary prosthesis is commonly relatively large compared to conventional syringes, a number of syringe injections are required, usually achieved by the repeated refilling of one syringe as opposed to the use of a plurality of prefilled syringes. Thus, to accurately control the amount of fluid being used to inflate the prosthesis, the syringe must not only be accurately and repetitively refilled, but the surgeon must count the number of syringe injections for each prosthesis. While the count is not large in itself, the environment and other things needing or diverting the surgeon's attention can easily result in an error in the count of syringe injections used to fill any particular breast prosthesis. Further, manually injecting all of the fluid from a filled syringe a number of times for each breast prosthesis can be fatiguing for the surgeon, and time consuming as thumb pressure on the syringe wanes over a period of time. Of course the longer the inflation takes, the longer the incision is open and the greater the risk of infection. Further, of course, the refilling of the syringe itself can be fatiguing and offers the possibility of intrusion and contamination by bacteria and other foreign matter. Finally, it is not uncommon for the surgeon or assistant to fill the syringe from an open bowl of the filling fluid, perhaps making the filling of the syringes a little easier, but enhancing the possibility of intrusion of bacteria and other contamination into the inflation fluid.
In the case of tissue expanders, the same are normally surgically inserted into the region desired in a substantially uninflated state, and the incision allowed to heal. Thereafter, the tissue expander is itself expanded by injecting fluid through a filling port on the tissue expander using a conventional hypodermic needle passing through the skin of the patient. The tissue expander frequently is not inflated to the desired final state of inflation in a single injection, but rather is inflated through smaller periodic injections extending over a significant period of time so that the tissue is gradually stretched or expanded to achieve the desired result. Obviously, a very large number of very small expansion increments would be ideal, but this would take an excessive amount of time of the doctor and patient alike, and unnecessarily extend the total inflation time. On the other hand, typically there is a limit to the amount the tissue expander can be inflated at any one time without causing pain to the patient, and perhaps injury to the tissue itself, so that typically some number of inflation increments are required to ultimately achieve the desired result. Since the pain or discomfort experienced by the patient generally relates to the pressure in the tissue expander, each filling increment could be limited to a pressure approaching, though below the recognized threshold of pain or discomfort by the patient if the pressure within the tissue expander could be measured. However, since conventional syringes have no pressure measuring capability, and to achieve substantial flow rates the pressure within the syringe body itself is purposely made substantially higher than the threshold of pain by the thumb pressure of the doctor, current practice is to add fluid to the tissue expander until the patient is conscious of the onslaught of discomfort or pain, ultimately limited, of course, to the desired expansion of the tissue expander for aesthetic or other purposes. Syringes having a pressure measuring capability are known, but such devices are of a high, not low pressure capability, being used to inflate collapsible but substantially inelastic balloons such as prostate dilation balloons.
In the case of both tissue expanders and inflatable breast prostheses, it would be desirable to be able to inflate the same rapidly, accurately, with minimum chance of infection or foreign matter intrusion, and without inflation to a pressure that induces pain or discomfort to the patient.